This invention relates in general to bearing seals and more particularly to seals which have the capacity to activate speed sensors.
Antilock brake systems, which are found on many automobiles and trucks of current manufacture, require devices at the road wheels for sensing the angular velocities of those wheels. On any vehicle so equipped, the speed sensing devices generate signals which are monitored by a processor that in turn controls the braking forces applied to the wheels, the object being to keep all four wheels rotating at the same velocity, even though one of the wheels may be rolling over a surface that offers considerably less frictional resistance than the surface over which the other wheels are rolling.
The typical speed sensing device includes an encoder ring which rotates with the road wheel that is to be monitored and a sensor which is excited by the encoder ring in the sense that it produces a pulsating electrical signal which reflects the angular velocity of the ring. To this end, the ring, which is formed from a ferrous metal, has discontinuities in the form of teeth or apertures that disrupt a magnetic flux upon rotation of the ring. The sensor responds to the periodic disruptions and delivers a signal, the frequency of which is proportional to the angular velocity of the ring and road wheel.
Typically, the nondriven wheels of an automotive vehicles are attached to hubs which rotate about spindles that are fixed in the sense that they do not rotate, there being wheel bearings between the spindles and hubs. If the vehicle is equipped with an antilock braking system, the encoder rings for these wheels are normally fitted over the hubs. But space is limited in the region of the bearings and hubs, and the encoder rings and the sensors represent unnecessary protuberances in these confined spaces.
The present invention resides in a seal which provides a highly effective barrier for excluding contaminants from and for keeping lubricants within the interior of an antifriction bearing, yet further serves as an encoder ring for activating a speed sensor. As such, the encoder ring and speed sensor easily fit the highly confined region surrounding the hub.